As far as I can tell, the attached file does not contain "±" but the characters 0x81 (not printable) and a "}", the latter which is causing the crash:
"}" is ending a formatting group without previously starting a formatting group with "{".

The crash will be fixed for the next release, but the text will not show anything as 0x81 is not a printable character and "}" is part of the formatting. Do you have a more complete example with more context?

[How to investigate the problem area]
1.Investigate the problem while erasing the entities one by one.
2.The content of the last entity is "± 1.0"
3.Execute 2 patterns leaving only "±" or "1.0".
"1.0" -> File Open and Convert(dwg2pdf) Success.
"±" -> Crash